1. Field of the Invention
Embodiments of the present invention generally relate to data processing, and more particularly, to techniques for composing queries with dictionary term criteria conditions.
2. Description of the Related Art
Databases are well known systems for storing, searching, and retrieving information stored in computer systems. A particularly common type of database is the relational database, which stores data using a set of tables that may be reorganized and accessed in a number of different ways. Users access information in relational databases using a relational database management system (DBMS).
Each table in a relational database includes a set of one or more columns. Each column typically specifies a name and a data type (e.g., integer, float, string, etc.), and may be used to store a common element of data. For example, in a table storing data about patients treated at a hospital, each patient might be referenced using a patient identification number stored in a “patient ID” column. Reading across the rows of such a table would provide data about a particular patient. Tables that share at least one attribute in common are said to be “related.” Further, tables without a common attribute may be related through other tables that do share common attributes. A path between two tables is often referred to as a “join,” and columns from tables related through a join may be combined to from a new table returned as a set of query results.
Queries of a relational database may specify which columns to retrieve data from, how to join the columns together, and conditions (predicates) that must be satisfied for a particular data item to be included in a query result table. Current relational databases require that queries be composed in complex query languages. Today, the most widely used query language is Structured Query Language (SQL). However, other query languages are also used. An SQL query is composed from one or more clauses set off by a keyword. Well-known SQL keywords include the SELECT, WHERE, FROM, HAVING, ORDER BY, and GROUP BY keywords. Composing a proper SQL query requires that a user understand both the structure and content of the relational database as well as the complex syntax of the SQL query language (or other query language). The complexity of constructing an SQL statement, however, generally makes it difficult for average users to compose queries of a relational database.
Because of this complexity, users often turn to database query applications to assist them in composing queries of a database. One technique for managing the complexity of a relational database, and the SQL query language, is to use database abstraction techniques. Commonly assigned U.S. Pat. No. 6,996,558 (the '558 patent) entitled “Application Portability and Extensibility through Database Schema and Query Abstraction,” discloses techniques for constructing a database abstraction model over an underlying physical database.
The '558 patent discloses embodiments of a database abstraction model constructed from logical fields that map to data stored in the underlying physical database. Each logical field defines an access method that specifies a location (i.e., a table and column) in the underlying database from which to retrieve data. Users compose an abstract query by selecting logical fields and specifying conditions. The operators available for composing conditions in an abstract query generally include the same operators available in SQL (e.g., comparison operators such as =, >, <, >=, and, <=, and logical operators such as AND, OR, and NOT). Data is retrieved from the physical database by generating a resolved query (e.g., an SQL statement) from the abstract query. Because the database abstraction model is tied to neither the syntax nor the semantics of the physical database, additional capabilities may be provided by the database abstraction model without having to modify the underlying database. Thus, the database abstraction model provides a platform for additional enhancements that allow users to compose meaningful queries easily, without having to disturb existing database installations.
However, even though the database abstraction model can simplify the use of an underlying database, it can nonetheless be very complex, particularly when it includes a large number of logical fields. One approach to simplifying a database abstraction model is the use of model entities, which provide an entity focus for abstract queries. For example, commonly assigned U.S. Pat. No. 7,054,877 (the '877 patent) entitled “Dealing with Composite Data through Data Model Entities” discloses the use of model entities to provide a focus for abstract queries. The '877 patent discloses query interfaces configured to enable a user to compose abstract queries from logical fields of the database abstraction model, and to specify a model entity to provide a focus for the composed abstract query.